In truth, everything is manifested, so to speak. Energy becomes things as matter densifies. What you are really asking is how can you “consciously create circumstances” and things.
There are many things that affect manifestation, which is a natural process. Beliefs, limitations, etc. What might be easy for someone who has years of practice might be difficult for another, and vice versa. Some do it on the first try.
Also just knowing how to do something doesn’t actually do it. Practice energy conversion (some people start with manifesting a parking place). Look into the works of Neville Goddard.
It’s always odd when people take natural phenomena and try to turn it into a commercial enterprise. Complicates the heck out of it.
The Esoteric Arts Guild put out a release called Potion of Manifestation, and I can attest to the fact that it works (I play it a lot!). Learning to get more conscious control over natural phenomena becomes effortless with morphic fields. We are truly blessed here.